JPS6393205A - Digital control type temperature compensating crystal oscillator - Google Patents

Abstract

PURPOSE:To improve the correction accuracy without increasing the capacity of a memory by using compensation data of temperatures at least two points near the temperature from a temperature sensor out of temperatures, which are stored in a semiconductor memory, to obtain compensation data of the temperature by interpolation. CONSTITUTION:A semiconductor memory 23 has addresses AD0, AD1-ADK and compensation data having outputs D0, D1-DI are stored in this memory 23. A calculating circuit 24 performs the calculation based on interpolation in accordance with temperature data A0, A1-AK, temperatures at least two points near these temperature data, and compensation data which correspond to these temperatures and are stored in the memory 23. A decoder 25 decodes the output of the calculating circuit 24 to output control signals of switching transistors 271-27n. Thus, the temperature resolution is practically improved without increasing the capacity of the semiconductor memory 23 to perform temperature compensation.

Description

[Detailed description of the invention] [Usage field on ffl page] The present invention is directed to a digitally controlled temperature compensated crystal oscillator.

[Conventional technology]

A conventional digitally controlled temperature compensated crystal oscillator has a configuration as shown in FIG. That is, the temperature information sent from the temperature sensor 1 is rounded by the digital conversion circuit 2 to a resolution equal to the temperature resolution stored in the semiconductor memory, digitized, becomes an address of the semiconductor memory, and is compensated from the semiconductor memory 3. data is outputted and decoded by the decoder 5 to control the capacitor switching transistors 7-, , 'l, . . . 7-n.

[Problem that the invention seeks to solve]

However, conventional digitally controlled temperature compensated crystal oscillators
There are limits to increasing the capacity of semiconductor memories due to cost and technical aspects. In addition, the 8 layers of semiconductor memory are
10 degree range and temperature resolution (proportional to Jl. Therefore,
Once the operating temperature range of the digitally controlled/1-degree water-captured oscillator and the eight semiconductor memories were determined, the temperature resolution was also determined. In other words, the capacity of semiconductor memory f
l (address) is 100, operating hot water temperature range is 120°C
Assuming 100°C up to ~80°C, the temperature resolution is
100÷100=1°C/address, and the temperature is corrected in steps of 1°C, which determines the correction accuracy.
This has caused the problem that the necessary finer correction accuracy cannot be obtained. SUMMARY OF THE INVENTION The present invention aims to solve these problems, and its purpose is to improve the correction tli U without increasing the capacity of the semiconductor memory.

[Means for solving the problem] The digitally controlled temperature-compensated crystal oscillator of the present invention has a digital control type temperature-compensated crystal oscillator in which data for compensating (, 1) the temperature characteristics of a crystal pendulum is recorded in a semiconductor memory. In a controlled temperature compensated water product oscillator circuit,
Compensation data for the temperature sent from a temperature sensor with a finer temperature resolution than the temperature step corresponding to the data is stored in the semiconductor memory, and the temperature sensor It is characterized in that it is obtained by interpolation using compensation data of at least two or more points close to the temperature sent from the system, and is compensated by 4 degrees.

[Effect]

According to the above configuration of the present invention, the temperature correction data not stored in the semiconductor memory is corrected for at least two temperatures closest to the temperature stored in the semiconductor memory without increasing the capacity of the semiconductor memory. 2. Increase the temperature resolution by finding it by interpolation using 11 data, /! This means that you can be compensated for it.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 shows an example of a configuration diagram of a digitally controlled zero-compensation crystal oscillator according to the present invention. 21 is a temperature sensor, 22 is a digital conversion circuit that converts temperature information into digital signals of A, , A, ...Ak, and 23 is an address with ADo, A
Dl...has ADk, and outputs Dyu%DI...D+
a semiconductor memory in which compensation data having a value of 2 is stored;
4 is a calculation by interpolation from temperature data A, , A, . The calculation circuit 25 is a decoder 26-, which decodes the output of the calculation circuit 4, that is, the compensation data D0, D, . ．．
2G-, ...26-〇 is a compensation capacitor, 27-,
．． 2'l, . . . 27-n are switching transistors that control the compensation capacitors, 28 is a feedback resistor in the crystal oscillation circuit, 29 is an oscillation inverter, 30 is a drain resistor in the oscillation circuit, 31 is a crystal resonator, 32 is a gate capacitance in the oscillation circuit, and 33 is a drain capacitance in the oscillation circuit.

FIG. 2 shows the frequency-temperature characteristics of the crystal oscillation circuit when the frequency (r, ) at 25° C. is used as a reference. Figure 3 shows the frequency characteristics depending on the number of turned on capacitors.The temperature ranges from 25°C to T.

If it changes to C, then from Figure 2 the frequency is Δf+
Ppm changes. Therefore, from FIG. 3, -Δr.

By finding the number n+ of compensation capacitors for changing the ppm frequency, the compensation data for T and 'C can be found. By performing the same calculation at each temperature, compensation data at each temperature, that is, the number of compensation capacitors to be turned on, can be obtained. Consider the case where the semiconductor memory contains compensation data for each step ①@C. FIG. 4 is an enlarged view of a part of FIG. 2. At 25°C, Δf is 099 m. At 126°C, Δf is -2 ppm, and the compensation data at each temperature is n/
2, (n/2+4). The temperature ranges from 25°C to T, (
25.degree. C.), the compensation data corresponding to T is not written in the semiconductor memory. Therefore, T
The temperature closest to i and stored in the semiconductor memory is
25° C. and 26” C, and the compensation data corresponding to these temperatures are n/2 and (n/2+4). Compensation data for T is determined from this data using the interpolation method of numerical analysis. As is generally known, the first-order interpolation formula is as follows, so X+ = 26, Xl+ = 25, x = 25.25, y.

= n/2, V+ = n/2 + 4, = n/2
It becomes +1.

Therefore, the compensation data at T is calculated as n/2+1. Compensation data can also be obtained by similarly calculating other temperatures that are not written in the semiconductor memory. In other words, it is possible to improve the correction accuracy without increasing the capacity of the semiconductor memory.

In the above example, it was determined using a first-order interpolation equation, but in order to increase the precision of the total p, it can also be determined using a second-order, third-order, etc. interpolation equation. In that case, it goes without saying that the number of data required for calculation is 3.4 at a temperature close to T7.

〔Effect of the invention〕

As described above, according to the present invention, the compensation data for the temperature sent from the temperature sensor having a temperature resolution superior to that of the temperature stored in the semiconductor memory is transferred to the temperature fm recorded in the semiconductor memory. In particular, we have adopted a configuration in which compensation data for at least two temperatures closest to the temperature sent from the temperature sensor is used to obtain compensation through interpolation, which improves compensation accuracy without increasing the capacity of semiconductor memory. This effect exists.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a digitally controlled/A degree compensated crystal oscillator of the present invention. Figure 2 is a frequency-temperature characteristic diagram of a crystal oscillation circuit. Figure 3 is a frequency characteristic diagram depending on the number of compensation capacitors. Figure 4 is a frequency-temperature characteristic diagram of a crystal oscillation circuit around 25°C. FIG. 5 is a configuration diagram of a conventional digitally controlled temperature compensated crystal oscillator. 1...Temperature sensor 2...Digital conversion circuit 3...Semiconductor memory 5...Decoder 6-+, 6-x, =・8-n? In compensation capacitor 1-1.1-*...7-n Switching transistor 8... Feedback resistor 9... Oscillation inverter 10... Drain resistor 11... Crystal oscillator 12... Gate Capacitance 13...Drain capacitance A;, A,...Ak Hot water temperature information converted into digital signals AD, , AD, , AD, Semiconductor memory address signals MDo, MDl, MDn Semiconductor memory output signal Do N Dr-Dn? IIi compensation data G,,G
,...Gn Signal for controlling the switching transistor 21...Temperature sensor 22...Digital conversion circuit 23...Semiconductor memory 24...Calculation circuit 25...Decoder 26-126-2.2 f3- n...Compensation capacitor 27-1.27-2.27-n...Switching transistor 28...Feedback resistor 29...Oscillation impark 30...Drain resistor 31...Crystal oscillator 32...Gate capacity 33...Drain capacity or more

Claims (1)

[Claims] In a digitally controlled temperature compensated crystal oscillator whose semiconductor memory stores data for compensating the temperature characteristics of the crystal resonator, the temperature has a finer temperature resolution than the temperature step corresponding to the compensation data stored in the semiconductor memory. Compensation data for the temperature sent from the sensor is obtained by interpolation using compensation data for at least two or more temperatures that are close to the temperature sent from the temperature sensor among the temperatures stored in the semiconductor memory. A digitally controlled temperature compensated water oscillator characterized by temperature compensation.